FAR 23.2505 — Equipment Function
FAR 23.2505 requires that every item of equipment installed on a Part 23 airplane must function as intended. Quick study guide for pilot students.
FAR 23.2505 is a short but foundational airworthiness rule under Part 23 (Airworthiness Standards: Normal Category Airplanes). It states that when installed, each item of equipment must function as intended.
In plain terms: if a piece of equipment is put on the airplane — whether it's required by regulation or added as optional gear — it has to actually do its job correctly. The manufacturer (and later, anyone modifying the airplane) cannot install equipment that is broken, mis-wired, incompatible, or that interferes with other systems.
Why it matters operationally:
- It supports the broader airworthiness concept: the airplane must conform to its type design and be in a condition for safe operation.
- It underpins inoperative equipment rules (like 91.213) — if something is installed, it's expected to work, and if it doesn't, you must address it before flight.
- It applies to all installed equipment, not just items required by the certification basis or operating rules.
For pilots, this rule is the certification-side reason your preflight and squawk discipline matter.